The assembly line remains a conventional basis of manufacturing. A product being assembled moves along the line from station to station. Workers at the stations add parts to the overall assembly (or to a sub-assembly) as the piece moves past them. The process is referred to as fixed if the same part or parts are added at each station.
Changes in customer demand have resulted in at least a partial shift toward flexible manufacturing, where at each station of the line the parts added to the assembly (or sub-assembly) vary. This facilitates manufacture of build-to-order products, such as computers. For example, the same assembly line can be used to produce a workstation having an extra-powerful processor, followed by one having a conventional processor but extra memory. To achieve this, a pick list can be generated as each new order is received. This serves as a guide to stock room personnel in gathering parts that will be used during assembly. And it may serve as a guide to workers on the line who assemble the order.
Flexible manufacturing can be inefficient. Pick lists may be generated or filled in a haphazard, error-prone manner. Assembly line workers may ignore order details and, simply, try to “use up” all parts presented to them from the stock room. Either way, assembly is slowed and quality degraded. The significance of these problems is heightened by today's marketplace, which demands high mix, low volume lines that produce with high yields. The complexity of the underlying products only worsens the issue.
There is thus a need for improved methods and apparatus for flexible and fixed manufacture. Such is an object of the invention. Another object of the invention is to provide such manufacture methods and apparatus that improve the cost, quality, repeatability, and cycle time of manufacture. Yet, another object is to provide such manufacture methods and apparatus that so improve the parts picking and assembly phases of manufacture. A still further object is to provide such manufacture methods and apparatus that facilitate the manufacture of complex high mix, low volume product lines.